In recent years, communication systems have introduced many new services for consumer user. For example, a voice mail system is used to provide a voice messaging service to the calling party when the called party is unavailable. More particularly, leaving a voice message for a called party is in widespread use in the case of a non-completed telephone call (e.g., where the called party is either busy or otherwise unavailable). Voice messages may in fact be more efficient than telephone conversations where participation of the two parties to a call is not really required to transfer simple information. Voice messaging can be considered a replacement for a human attendant who would otherwise be required to transcribe the message, or for a simple analog recording device (answering machine) that can be connected to a called telephone.
This feature is offered by the telephone service providers both for the fixed line telephone and for the mobile telephone networks (GSM, GPRS, UMTS, . . . ). Therefore, it is important to offer to the users of such fixed or wireless terminal equipment means by which they can be notified as soon as the Voice mail has been read by the called party.
Referring to FIG. 1, the infrastructure of voice carriers today is based on hierarchical circuit equipment (TDM), with Local Exchange Switches (Class-5) 110 managing voice services for telephone with answering machine 100 and the Transit Switches (Class-4) 120 managing call routing.
The Local Exchange Switch 110 is a complex device handling 3 main tasks; namely: (1) subscriber connectivity to the provider network via analog or ISDN lines; (2) delivery of phone services such as dial tone, digits analysis, Call Detail Records generation, call waiting, call transfer, call conferencing, caller ID, etc.; and (3) connectivity to the core network of the provider with transit/tandem switching functions (Class-4) and network signalling (SS7).
Next Generation Networks (NGN), which are the new communication network architecture, are shown in FIG. 2. The principle is to use packet mode transmission technologies, reserved up till now for data, to transport all the various types of telecommunication services. In addition, interfaces are separated from the different layers of the communication network (transmission layer 220, control layer 210 and service layer 200) to allow for a greater evolution of the network. Finally, NGN uses the new packet technologies to offer broad band services.
The NGN includes in the service layer 200 a central service server 201, and in the control layer a media gateway controller 211. The transport layer 220 includes an IP Switch core network 225 which is connected to a signaling gateway 230. The IP Switch core network 225 includes connections to a Digital Subscriber Line Access Multiplexer (DSLAM) 240, a content transmission management system (CMTS) 250, and voice over IP (VoIP) 260 connection. The signaling gateway includes connection to the Public Switched Telephone Network (PSTN) 235 by SS7 to other telcos and ISDN PRI to a customer PBX. This type of system includes all the normal types of services and applications available to a user, for an example voice mail, call waiting, caller ID etc.
The voice mail system operates to give messages to a user that a person has called and then the user contacts the person who made the call at a time which is convenient to the user. Sometimes the user forgets to call or just doesn't bother to call.
The person who made the call may call several times in case the person has missed a reply or if the person needs an urgent reply. The person making the call has no way of knowing if the user has listened to voice mail or read another type of mail.